NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 25 



Type: Holotype is Mason 23, June 1925, on sheet 173637 in the 

 Herbarium of the California Academy of Sciences, San Francisco, Calif. 

 An isotype fragment is on sheet 8790 in HAHF. 



Type locality: Epiphytic on Dictyota masonii, Isia Clarion, 

 Revillagigedo Archipelago, Mexico. 



Acrochaetium punctatum sp. nov. 

 Plate 2, fig. 1 



Thallis 100-300 ju, altis, ope unicae cellulae basalis 9-12 /t diametro 

 ad superficiem adnexis, aliquot filamenta curva 6-7 /x, diametro, multas 

 breves, secundas ramulas in latere convexo edentis; cellulis iisdem vel 

 etiam duplis longitudine quam latitudine, brevioribus in partibus infer- 

 ioribus, singulatim unicum prominens distale pyrenoide habentibus; an- 

 theridiis in ramulis brevibus, secundis. 



Thalli epiphytic, 100-300 /* high, attached superficially by a single 

 somewhat enlarged basal cell 9-12 jx. in diameter giving rise to several 

 curved, erect filaments 6-7 ft in diameter with numerous short, secund 

 branchlets on the convex sides; cells 1-2 times as long as broad, the 

 shorter ones in lower parts, with a parietal chromatophore and a single 

 prominent discoid pyrenoid situated in the distal portion of the cell; 

 reproduction sexual ; antheridia borne on the short secund lateral branch- 

 lets ; carposporic plants not seen. 



Type: Holotype is Dawson 462b, Feb. 12, 1946 in vial 1623 and 

 on slides 929-931 in HAHF. 



Type locality: Epiphytic with Kylinia secundata on the "leaves" 

 of Sargassum, rocky south shore of Bahia Bocochibampo, Sonora, Mexico. 



This species belongs to Papenfuss' Group I of Acrochaetium, but 

 does not seem to agree with any of the known species listed by him. 



Acrochaetium hancockii (Dawson) Papenfuss 

 Plate 12, fig. 2 



Papenfuss, 1945, p. 306. Rhodochorton hancockii Dawson, 1944, p. 

 255, pi. 41, figs. 4-6. 



Thalli epiphytic, attached to the host by a single unenlarged basal 

 cell; erect filaments abundant and very close together, cylindrical, slen- 

 der, 500-1500 IX long, 5-7 ju, in diameter, slightly attenuated to the apices, 

 with cells 3-4 diameters long; sterile filaments rarely or almost un- 

 branched in some specimens, more frequently in others ; fertile filaments 

 more frequently branched, with short lateral, secund branchlets in series ; 



